The present invention relates generally to computer systems and in particular to optical alignment in a fiber optic transceiver.
Single and multiple lens array fiber optic transceiver devices require precise optical component to fiber alignment for optimal function. The devices may include optical laser and/or photodetector components each coupled to a distinct optical fiber through a lens assembly. The alignment process generally involves adjusting a laser light beam path from an optical fiber or laser to a receiving photodetector or optical fiber element, respectively. The typical optical alignment tolerance for a 62.5 micron diameter fiber using a lens array is on the order of only plus or minus 5 microns. Thus, alignment considerations are essential in the design and assembly of fiber optic transceiver devices.
Two distinct methods are known for aligning optical laser and photodetector component devices to their corresponding fibers, active and passive alignment. Active alignment utilizes the laser component in an active state at a sub-assembled stage of the device. Once the laser is activated, the optical elements (laser photodetector components, lens assembly, and fiber optic cable) are moved in a lateral plane (orthogonal to the optical path) while a photoreceiver input is monitored to establish maximal light throughput intensity. After the light throughput is optimized, the individual elements are mechanically fixed to one another to maintain alignment. This procedure allows for the precise alignment of the optical elements. Current active alignment procedures, however, typically require numerous and expensive components needed during a multi-step alignment process. For example, the optical elements must all be manipulated separately to achieve proper alignment.
Passive alignment typically involves manufacturing the transceiver elements affecting the optical path to very high tolerances. This method allows for the optical alignment of the transceiver devices without monitoring laser throughput and performing the multiple-step alignment procedure. The high tolerances required for passively aligned transceivers, however, may complicate their design and increase manufacturing time and cost.
Therefore, it would be desirable to provide optical alignment in a fiber optic transceiver that would overcome the aforementioned and other disadvantages.
One aspect of the present invention provides alternative methods for aligning a fiber optic cable with optical components on a device carrier through an intervening fiber optic lens assembly. At least one optical component, such as a laser and/or photodetector, and at least one electrical component, such as a laser drive amplifier and/or transimpedence amplifier, is attached to the device carrier. The lens assembly may include a single lens or a multiple lens array. The alignment process begins by fixing the lens assembly with respect to the fiber optic cable (with a plurality of pins and/or retention clips), in a first method, or fixing the lens assembly with respect to the device carrier (with a plurality of pins and/or an adhesive), in a second method. Light, which may be provided by a laser device attached to the device carrier, is then sent through the composite. The lens assembly with fixed fiber optic cable is moved with respect to the device carrier in the first method. The lens assembly with fixed device carrier is moved with respect to the fiber optic cable in the second method. The movement may angle a laser beam path from an optical centerline. The light sent through the composite is monitored thereby facilitating channel throughput optimization. The movement of the lens assembly is then fixed with respect to the device carrier, in the first method, or is then fixed with respect to the fiber optic cable, in the second method, according to the monitored light.
Another aspect of the present invention provides aligned transceiver assemblies having a fiber optic cable, device carrier, and fiber optic lens assembly having features that facilitate alignment and fixing according to the invention methods.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention, rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.